docs: def reportProgress(self, state, action, text=None, tick=None):
          """ If we want to keep other code updated about our progress.
  
              state:      'prep'      reading sources
                          'generate'  making instances
                          'done'      wrapping up
                          'error'     reporting a problem
  
              action:     'start'     begin generating
                          'stop'      end generating
                          'source'    which ufo we're reading
  
              text:       <file.ufo>  ufoname (for instance)
              tick:       a float between 0 and 1 indicating progress.
  
          """
          if self.progressFunc is not None:
              self.progressFunc(state=state, action=action, text=text, tick=tick)